That's interesting that the hunt club actually goes so far as to recommend them, though it's true that a horse that can actually safely hunt in a snaffle is a very, very rare thing indeed. There's an old hunting expression "Fools, ****ed fools and people who hunt in snaffles." I had a sweet, wonderful beginner school horse, a QH mare, that would hunt in a snaffle, but she'd be fussy and root at the reins and fidget at the checks. It was actually easier to hunt her in a pelham as she had complete respect for it. I never actually had to use the full effect of the pelham with her and could keep the curb rein loose the entire time, but I simply never found a snaffle she'd hunt in.
leverage single bit I would rather use my ported kimberwick.
This statement confuses me. A pelham is ridden with two reins, a snaffle and a curb. The snaffle rein connects directly to the bit and the curb connects to the bottom of the shank. It is absolutley the rider's choice if and when to engage the curb; the pelham can be ridden on the snaffle rein with just the effect of the snaffle mouthpiece. They also come in a variety of mouthpieces; you can choose one that's close to what you normally hack in. It's not uncommon to see foxhunters knot the curb rein and leave it on the horse's neck, and pick up the knot when they need emergency brakes.
A kimberwicke, on the other hand, always has some curb action as it only has one rein, and the port makes it a little harsher. While it's true you can adjust the severity of a kimberwicke by moving the rein position; you make that adjustment once, before you tack up and pretty much must ride with it for the rest of the day.
The most common reason you hear for kimberwickes over pelhams is that the rider doesn't want to cope with two reins. Since you're considering a double, clearly that isn't the issue. I strongly prefer the pelham for the flexibility.
Whatever you choose, make sure you hack out in company with that bit a few times before hunting in it.
Please also consider a poster/advice giver's knowledge or experience foxhunting when evaluating their advice; if you've never been hunting, it's hard to imagine the experience or the effect it has on an otherwise perfectly behaved horse.